tundra i dont dispute as its been stated, fall 2021 is release of new tundra as 22MY

23MY/24MY 4runner would put the current 5th gen at 14/15 yrs old which would push it to the same as age the current 2nd gen tundra at 15 yrs old.

24MY/25MY tacoma would put that gen at a young generation at 8/9 yrs old which contradicts toyota extending out a generation to 10-12 yrs old. i can see a mid cycle refresh at 21/22MY (6yrs) like they did on the 4runner at 14MY (6yrs)

the tundra is an odd ball as it has gone thru 2 mid cycle refreshes at 2013 (14MY) (8yrs) and 2017 (18MY) (10yrs)

as far as the engine, i expect it to be the 3.5 v6 from the tacoma just geared different and different engine output just like they did for the 4.0 in the tacoma and 4runner (see 2012 tacoma 4.0 v6 vs 2014 4runner 4.0 v6)

but who knows what toyota is doing since they pretty much can keep a secret better than most on internals compared to most oem's.

best bet is to watch for announcements during the feb car show which i think is the chicago car show. that is when toyota lately has been announcing new generations compared to the old days when they announced them during jan car show